with cornerback Shareece Wright in one-on-one drills. It is a cruel twist of fate for the 24-year old Alexander, who has overcome a string of injuries to his other knee and is coming off the most productive season of his NFL career.

Alexander, who is listed at 6 feet 5 and 217 pounds, caught 37 passes for 658 yards and seven touchdowns last season, all career highs.

Alexander’s history of knee injuries – he has had five surgeries dating back to his time at Missouri – caused him to go undrafted in 2010, despite a senior season at Missouri in which he caught 113 passes for 1,781 yards and 14 touchdowns and was named an All-American.

Alexander eventually latched on with the St. Louis Rams, for whom he caught a total 46 passes for 737 yards and three touchdowns in two seasons before he was released last August. The Chargers signed him in October, and he proceeded to post his career-best totals in only 10 games.